Below ground swimming pool

ABSTRACT

A plurality of preformed modular, thermoplastic panels are solvent welded to each other to form a unitary swimming pool structure in place in an excavation only slightly larger than the final pool dimensions. Vertical stiffener ribs previously solvent welded to the outside of the walls of the pool are utilized to stiffen the walls and to anchor them by passing reinforcing bars therethrough. The bars are anchored into the ground. To join abutting vertical edges of adjacent panels, an elongated clamp is used to hold the panels and an overlying weld plate during the hardening of the solvent weld. This clamp is in two severable parts including an outside plank member having upper and lower legs which are temporarily clamped to cooperating legs of an inside plank member respectively above and below the panels. After the weld is complete and the clamp removed, adjacent ribs and reinforcing bars on either side of the vertical weldment are at least temporarily encompassed by a vertical concrete form and concrete is poured therein to additionally strengthen the bond between the panels. A finish coping is positioned around the top edge of the pool and has a flexible downwardly extending plane so that the bottom flange edge rests in generally sealing relation to the top edge portion of the vertical pool wall even though there are minor undulations in this top edge portion.

[ June 19, 1973 BELOW GROUND SWIMMING POOL [57 ABSTRACT A plurality of preformed modular, thermoplastic panels Inventor: Irving H. Posnick, Minneapolis,

Minn.

are solvent welded to each other to form a unitary swimming pool structure in place in an excavation only c n I m i M PM o m he an wm AM a e n m S s A H 7 slightly larger than the final pool dimensions. Vertical [221 Filed: June 1971 stiffener ribs previously solvent welded to the outside 2 Appl, 153 177 of the walls of the pool are utilized to stiffen the walls and to anchor them by passing reinforcing bars therethrough. The bars are anchored into the ground. To

join abutting vertical edges of adjacent panels, an elongated clamp is used to hold the panels and an overlying U.S Int. Field oi Search weld plate during the hardening of the solvent weld.

This clamp is in two severable parts including an out- References (med side plank member having upper and lower legs which UNITED STATES PATENTS are temporarily clamped to cooperating legs of an in side 'plank member respectively above and below the panels. After the weld is complete and the clamp removed, adjacent ribs and reinforcing bars on either side of the vertical weldment are at least temporarily encompassed by a vertical concrete form and concrete is poured therein to additionally strengthen the bond between the panels. A finish coping is positioned around the top edge of the pool and has a flexible downwardly extending plane so that the bottom flange edge rests in co 9 9999 3 6 6666 U H HHHH 6J2Mm2222 125 5555 .22... H 55 m n 4 Slaughter.;..................i.........

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FOREIGN PATENTS OR APPLICATIONS generally sealing relation to the top edge portion of the 975,604 11/1964 Great Britain 52/515 vertical pool wall even though there are minor undulations in this top edge portion.

6 Claims, 17 Drawing Figures Primary ExammerJohn E Murtagh Attorney-Bud, Braddock & Bartz BELOW GROUND SWIMMING POOL BACKGROUND OF THE INVENTION This invention relates to a below ground swimming pool and to a method and apparatus for its construction.

Below ground swimming pools are customarily constructed of poured concrete with or without ceramic tile supported on the poolside thereof; or of sprayed concrete or other material; or with side walls of concrete building block or the like. Such pools are either constructed with side walls and bottoms of water impervious character or are lined with water impervious liners of suitable materials such as, for example, vinyl. Such pools, while having great permanence, are extremely expensive to build initially. A major portion of the expense is the excavation necessary to receive the pool and the excavation necessary to accommodate the forms needed to construct the side walls of the pool. A further expense is the extensive backfilling needed to restore the ground level around the pool after the forms have been removed.

In order to make swimming pools, and all the healthful benefits thereof, available to a wider cross section of the populace, above ground pools have been devel-.

oped. These are generally less expensive to build initially due to use of relatively inexpensive thin side walls and because no substantial excavation is used. They fall generally into two categories. First, the generally smaller less permanent variety which must usually be erected and disassembled each season; and, second, the generally larger variety which is once erected and left in place from season to season.

A difficulty with both of these categories of above ground swimming pools is their generally unsightly appearance; and, consequently, their failure in many instances to conform to the zoning and other restrictions in residential areas. 7

A difficulty with above ground pools of the first category is that they are subject to extensive wear and tear in the process of taking them down, storing them in the off season, and reassembling them. Further, the side walls and supporting structures are often not sturdy enough to withstand the substantial wear and tear they are subjected to when the pool is actually in use. Because of the flimsy nature of the side walls, these pools cannot be left up and filled with water through the winter in most of the country because forces due to the formation of ice will tend to destroy the side wall supports and the side walls. This means that a very large volume of water must be run down the drain each year and must be drawn again to till the pool in the succeeding season.

The second category of above ground pools customarily includes wood or metallic side walls of substantial character sufficient to withstand the outward forces of the water therein. A watertight liner of vinyl or the like customarily covers these side walls and the bottom area of the pool. Either the bottom of the pool must be formed in concrete or other permanent building material in order to try to permanently establish the contour of the bottom, customarily including a deepened area to provide for clearance under a diving board; and/or the ground underneath the pool must be excavated and shaped to provide the desired contour.

In the case of such a permanent bottom surface, a substantial portion of the expense of building a below ground pool will have been spent without obtaining the advantages of a below ground pool.

In the case of a plain dirt bottom, it has been found that the surface water run-off both from natural precipitation and from splash over from pool use itself will enter the depression under the liner to occasion the build up of a puddle of water under this liner. This causes an erosion of the pool bottom to destroy the deepened area under the diving board, for example, and to generally lose the desired contour. Thus, a dirt pool bottom requires considerable and constant work from season to season to maintain its proper form and contour.

It has been found over the years that substantial lat eral support due to the mechanical strength of the wall of the swimming pool is not needed when a pool is located below ground. Typically, as long as the pool is kept full of water, the stresses from the outside and from the inside are substantially equalized even during the winter when a substantial portion of the water in the pool becomes frozen. This same situation obtains in the summer time when the outward forces due to the weight of the water in the pool are counteracted by the ground tightly backfilled against the walls of the pool.

It is, therefore, desirable to construct a swimming pool having the light and relatively inexpensive walls of the above ground pool in a below ground installation in an excavation which need be very little larger than the finished pool size.

BRIEF SUMMARY OF THE INVENTION:

According to the method of the invention, an excavation for a swimming pool is prepared which is only very slightly wider and longer than the predetermined dimensions of the finished pool. A plurality of preformed panels capable of being solvent welded to each other and to fittings of similar materials are assembled in the excavation and are solvent welded in fixed sealing relationship to each other. The vertical welds to bond abutting side by side panels are accomplished through the use of a weld plate of compatible material which is solvent welded to the preformed panels. This weld plate is clamped onto the adjacent abutting edges throughthe use of a novel clamp which includes an outside plank member of dimension to slide between the panels to be welded and the side wall of the excavation to take position in contact with the weld plate; and aninside plank member to be situated against the adjacent abutting ends of the panels to be welded. These two plank members having cooperating upper and lower legs which are temporarily clamped together until such time as the solvent between the two panels and between the weld plate and the two panels has sufficiently hardened so that the clamp can be released and the outside plank member removed from the area between the now welded panels and the side wall of the excavation.

According to one form of the invention, the pool bottom can be constructed of a plurality of plastic panels solvent welded to each other and similarly integrally joined with a fitting in the form of a slotted peripheral connecting strip which, in turn, is integrally bonded to the bottom edge of the vertical side wall panels, thus to form a watertight complete swimming pool structure.

According to other forms of the invention, the bottom edges of the vertical wall panels can be imbedded in a poured concrete floor thus sealing off the bottom the bottom edges of the vertical wall panels can be terminated at or below the bottom surface of the excavation, where that bottom surface is formed in the precise desired shape of the pool bottom, and the entire pool can then be lined with a suitable watertight plastic liner, for example a vinyl liner, to constitute the finished water retaining pool structure.

It has been found desirable to cap the vertical wall structure with a peripherally extending finish coping having an open, deck-receiving area defined by an upwardly and outwardly extending flange portion, the deck receiving area being of shape to receive either an edge portion of a poured concrete deck, or edge portions of deck materials such as patio brick, wood slats, and/or earth fill. Each run of coping is also provided with a downwardly extending flange in adjacent relationship to the top edge of its vertical side wall of the pool, the flange extending normally downwardly out of a vertical plane so that the bottom edge of the flange will rest in generally sealing relation to the top edge portion of the vertical pool wall even though there are minor undulations in this top pool wall portion. In the form of the invention as shown, the coping provides a space, between the deck receiving portion and a bottom flange supporting portion which is open toward the interior of the pool and which can be used to seal the top edge of a flexible pool liner into place should this be necessary or desirable.

The panels which are to become vertical wall panels are provided, before they are assembled into the pool, with a plurality of spaced vertical stiffener ribs which are solvent welded or otherwise made integral with the panels. In addition to stiffening the panels, these ribs are provided with openings to receive vertical reinforcing bars which can go clear through the ribs and into the ground at the bottom of the excavation. Horizontal openings are also provided in these ribs, and connections through these horizontal openings are used to tie the pool walls into the surrounding ground.

As shown, adjacent ribs and reinforcing bars on either side of a vertical weldment are at least temporarily encompassed by a vertical concrete form and concrete is poured into the form in surrounding relationship to the ribs and the reinforcing bars to additionally strength the bond between the panels and further stabilize the pool walls.

In the drawings:

FIG. 1 is a perspective view of a below ground swimming pool constructed in accordance with a first form of the present invention with portions of the surrounding ground and deck broken away for clarity;

FIG. 2 is a back outside elevational view of one of the modular panels of the invention before the end flanges are trimmed therefrom preparatory to welding it to an adjacent panel;

FIG. 3 is a horizontal sectional view taken on the line 3-3 in FIG. 2;

FIG. 4 is a vertical sectional view taken on the line 4-4 in FIG. 3;

FIG. 5 is a front, inside elevational view of the panel of FIGS. 2, 3 and 4;,

FIG. 6 is an enlarged horizontal sectional view taken on the line 6-6 in FIG. 1;

FIG. 7 is an enlarged horizontal sectional view taken on the'line 7-7 in FIG. I;

FIG.'8 is an enlarged vertical sectional view taken on the line 88 in FIG. I;

FIG. 9 is an enlarged vertical sectional view taken on the line 99 in FIG. 1;

FIG. 10 is also an enlarged vertical sectional view taken as if on the line 99 in FIG. 1 but showing a variant form of construction for the bottom wall of the pool;

FIG. 11 is likewise an enlarged vertical sectional view taken as if on the line 99 in FIG. 1 but showing yet another form of the invention in which a water impervious liner is used to seal the bottom of the pool;

FIG. 12 is an enlarged vertical sectional view taken on the line l2-l2 in FIG. 1;

FIG. 13 is also a vertical sectional view taken as if on the line 12-12 in FIG. 1 but showing a differentrelationship between the vertical panel wall and the coping;

FIG. 14 is likewise a vertical sectional view taken as if on the line l212 in FIG. I but showing a variant form of the invention in which a pool liner is fastened along the top edge of the pool into the coping;

FIG. 15 is a vertical sectional view through one of the panels and showing its relationship to a clamp for solvent welding, the clamp being shown in side elevational view;

FIG. 16 is an enlarged horizontal sectional view on the line 16l6 in FIG. 15; and

FIG. 17 is a fragmentary perspective view of two adjacent panels after the solvent weld illustrated in FIGS. 15 and 16 has been completed and the clamp removed therefrom.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

A swimming pool 20 includes a plurality of modular panels 22 of plastic material which has the property of being capable of being solvent welded to other plastic material. In accordance with a first form of the invention as disclosed in FIGS. 1, 6, 7, 8, 9, l2 and 17, these panels are joined together in end-to-end relationship and solvent welded to each other and to a weld plate 24 to constitute an apparently continuous strip of material in the vertical side wall of the finished pool. Adjacent panels are joined along their longitudinal edges by means of solvent welding or otherwise bonding into slotted fittings indicated generally at 26 to affect either planar or angular unions. As shown in these figures, the entire pool can be constructed of such panels and fittings, and a peripherally extending finish coping 27 can be fastened around the top edge portion of the vertical pool walls. As shown, this coping is solvent welded to the top edge of the top panels, but it could be bolted or screwed or otherwise mechanically fastened to such top edge portion.

To aid understanding the method of the invention, a typical modular panel 22 is illustrated in FIGS. 2 through 5. The size of such panels is a matter of choice, but panels 20 feet long and 40 inches high have been found to be convenient and useful. These panels can be made of thermoplastic material by the process known as vacuum forming. In this process, a suitable plastic sheet is heated and placed over a mold, and the air between the heated thermoplastic sheet and the mold is evacuated to pull the panel down to conform to the exact shape of the mold. Since a below-ground pool made in accordance with the present invention has side wall stability and strength and permanence approaching or exceeding that of a conventional cement wall, ceramic tile pool, the vacuum form mold is made as an exact negative representation of a ceramic tile wall. As a result, one side of the modular panel 22 exactly simulates the appearance of such a wall. This panel side will be the one contact with the water in the finished swimming pool. Throughout this specification, this side of each of the panels will be designated the front and the inside surface 29 of the panel. The side of the panel against which the backfill rests will be designated the back and outside surface 30 of the panel.

In the process of forming the panel 22, as the panel is drawn into the mold, a panel return flange, generally designated 28, is formed extending outwardly at right angles from the back, outside surface 30 of the panel 22. This flange extends peripherally around the entire panel and includes an upper lip 32, a lower lip 34 and end lips 36,36. These lips tend to stiffen the panel against bending. However, at certain positions within the finished pool, the presence of the lips is a disadvantage, and the lips can be removed by trimming or sawing. For example, as will be explained, when two verti cal panels are joined end-to-end, they .are solvent welded to each other in abutting, end-to-end relationship and to a weld plate which extends over the area where the end lips 36,36 would normally be positioned.

In order to utilize modular panels 22 to form the pool of the invention it is desirable, not only that they be of material which can be solvent welded to itself and to similar materials, but that the material be extremely tough, light in weight, and easily workable. One such material which has proved excellent for the purpose is acrylonitrile-butadiene-styrene (ABS). Panels, coping and fittings made with ABS can be readily solvent welded to each other, can be sawed to obtain desired configurations, and can'be heated and bent to obtain desired shapes. Obviously other materials could be used, including materials which can be solvent welded or otherwise permanently bonded to each other but which do not necessarily have thermoplastic properties.

After the panels as illustrated in FIGS. 2 through 5 are formed, those which are designed to eventually have an end for end planar or angular relationship to other similar panels can have their end lips 36,36 trimmed therefrom. This results in some loss of stiffness in the vertical direction, but this is more than overcome by the attachment to the back surface 30 of the panel by solvent welding or other usual or. preferred technique of a plurality of mutually parallel vertical stiffener legs 38 having vertical passages 90 provided therethrough.

To erect a pool in accordance with the first form of the invention as illustrated in FIG. 1 and other figures, an excavation is made at the desired location in the ground where the pool is to be situated. This excavation need be only very slightly wider and longer than the size of the finished pool. For example, a clearance of between 4 and 6 inches from the vertical side and end walls of the pool to the adjacent excavation wall will be sufficient.

In the pool of FIG. 1, modular panels 22 are utilized to enclose the entire bottom thereof; so the bottom of the excavation will preferably be shaped and contoured to exactly conform to the shape and contour of the desired pool bottom. Modular panels 22, to form a pool bottom wall 44, will be joined together using one of the longitudinal slotted fittings 26 in the form of a planar strip 40, as illustrated in FIG. 8 in connection with the joining of vertical side walls on another portion of the pool. The planar strip 40 is provided with a relief groove 42, and in order to accommodate the change in direction of the pool bottom from horizontal to sloping, the area in alignment with this groove 42 of the planar strip 40 can be heated and the strip bent to align the slots in the strip to receive the adjacent panels in the desired angular relationship to each other.

It should be understood that the modular panels 22 used to form the bottom wall 414 of the pool can have mutually parallel stiffener legs such as the vertical legs 38 illustrated in the drawings, or can be put together without the use of such stiffener legs.

The outer peripheral edges of the completely formed pool bottom wall 44 are permanently bonded to a fit ting 26 constituted as an elbow strip 46. This elbow strip 46 can be obtained either by extruding the fitting in shape shown in FIG. 9 or by heating the relief groove portion 42 of the planar strip 40 and bending it to form the shape as disclosed at 46 in FIG. 9.

While the pool 20 is illustrated as having a maximum depth of two courses of modular panels 22 and as having side walls of only two end-to'end panels in length and end walls only one panel in width, it is to be understood that pools in different even modular lengths and depths can be constructed using the method of the invention. Also, pools can be constructed to have one or more non-modular dimensions by the simple expedient of sawing or otherwise trimming the modular panels to result in a pool of the total desired dimension.

An additional procedure in constructing the pool consists of trimming the panels 22 which are to make up the bottom course of the vertical pool walls to remove the lips; and further trimming some of these panels along the bottom. This trimming will be done in such a'manner that when the panels of the bottom course are inserted and bonded into the elbow strip 46 at the proper location, the resulting top edges of the bottom course of panels will terminate in a horizontal plane. Elbow strip fittings 46 can be utilized to join adjacent panels 22 in each of the vertical comers of the pool; but to join coplanar end-to-end abutting panels 22, a special apparatus in the form of an elongated clamp 48 has been found useful to hold a weld plate 24 and the adjacent abutting ends of the panels in fixed re lationship to each other while the solvent welding pro cess is accomplished. This elongated clamp and the method of welding the panels :in end-to-end relationship will be subsequently discussed. It is sufficient to say at this point that once the lower course of panels are welded to form a continuous waterproof layer and are permanently bonded into the lower elbow strip 46 around the entire pool, a longitudinal slotted fitting 26 constituted as a planar strip 40 as indicated in FIG. 8 is bonded into position around the top edge of these lower course panels.

The next course of panels is suitably trimmed to re move lower lips 34 and end lips 36,36. Adjacent coplanar panels are bonded to each other and adjacent panels related at right angles are likewise bonded into the vertically positioned elbow strips 46 to form, with the bottom vertical wall course and the bottom wall 44 the permanent watertight swimming skin.

The topmost edge of the topmost course of panels forming the vertical pool walls will still include the upper lip 32. The finished coping 27 as clearly seen in FIG. 12, has a horizontal lower support wall 50 which,

as shown in that figure, is solvent welded to the upper surface of the lip 32. A flexible downwardly extending bottom flange 52 is integral with the inside edge of the lower support wall 50 and extends downwardly therefrom in a plane which normally is not vertical. Since there is an inevitable tendency on the part of the vertical side walls and particularly the upper edge portions of the upper course thereof to have minor undulations of the inside front surface 29, the lowermost edge portion of the bottom flange 52 is normally positioned out of a vertical plane with its upper parts in direction toward the excavated side walls. When fastening the coping to the top edge of the vertical side walls, as much as possible the coping is forced over until the relationship of the bottom flange 52 is exactly parallel to and in contact with the vertical front, inside surface 29 of the flange 22 as best seen in FIG. 13. When undulations occur, the panel 22 will be situated short of a position in contact with the entire outer surface of the bottom flange 52, and these parts will then be positioned as best seen in FIGS. 12 and 14. As shown, the flexibility and out-of-vertical normal configuration of this bottom flange 52 causes it to remain in apparent sealing relation to the surface 29 of the panel 22 in spite of these undulations.

The coping 27 is provided with a vertical upright leg 54 integral with and extending upwardly from an intermediate portion of the lower support wall 50. As shown, an open, deck-receiving area 56 is defined in the coping 27 by a curved top, deck-receiving flange 58 which is integral with and extends horizontally inwardly from a top portion of vertical upright leg 54, around a circle arc (as shown) to terminate in a top horizontal portion 60. The initial horizontal portion of the deck flange 58 is designated 62, and the portion connecting the lower and upper horizontal portions is designated 64.

As shown in FIGS. 1, 8 and 9, and as described above, the lower lip 34 of the panels which are to be joined in abutting end to end relationship can be removed. The upper lip of these panels in the lower course of panels can also be removed as described above and as illustrated in FIG. 8. Usually the upper lip 32 of the upper course of panels will not be removed as it is utilized in the bonding of the coping strip 27 to the upper edge of the vertical wall. It is to be understood, however, that situations can arise where it will be advantageous or necessary to bond panels 22 together in end-to-end relationship with the upper lip 32 and the lower lip 34 of each of the panels still intact.

This situation will arise where it is desired that the bottom edge of the pool itself be solvent welded along a lip 34 to a suitable plastic bottom material or where the lip 34 is to be retained on the bottom course to more firmly bond the panels into a cement bottom. This structure is shown in FIG. 10, and will be explained in detail later.

The method of bonding two panels in end-to-end relationship will be described as two panels in which the upper lips 32 and the lower lips 34 are intact and in which the end lips 36,36 have been removed. The method used when one or both of the upper or lower sets of lips was removed would be the same.

Method of Bonding Coplanar Panels in End-to-End Relationship.

Referring now specifically to FIGS. 15, 16 and 17, coplanar abutting panels 22,22 are placed in the desired relationship with respect to each other after a suitable solvent has been applied to their adjacent end edges. Solvent is applied to a suitable weld plate 24 and to appropriate areas of back surfaces 30 of the panels 22. The elongated clamp 48 is brought to bear on the inside front surfaces of the panels and on the outside back surface of the weld plate.

The clamping action on the inside front panel surfaces and on the outside back weld plate surfaces is actually maintained by inside plank or board 66 and an outside plank or board 68, respectively. Each of these boards or planks is attached to a corresponding channel iron, 70 and 72 respectively as by screws 74 extending through the channels and into the wood of the planks. Inside plank 66, its channel 77, and upwardly extending arm 76, and a pair of transversely extending studs 78,78 on a lower leg portion of channel iron 70 together from an inside plank member 80.

Outside plank 68, outside channel iron 72, an up wardly extending arm 82 integral with the channel iron 72, and a lower slotted extension arm 84 extending integrally from channel iron 72 together constitute outside plank member 86.

As previously stated, the side wall of the excavation is but 4 to 6 inches away from the desired final location of the vertical pool wall panels 22. The outside and inside plank members are separable from each other. The inside plank member will be placed in its approximate location against the inside front surfaces of the adjacent panel members 22, and the outside plank member will be turned at 90 from the position as seen in FIGS. 15 and 16, and will be slipped or slid between the vertical panel members and the wall of the excavation. When approximately in position, this outside plank member will be rotated 90 thus to position the lower slotted extension arm 84 under the panels and in position where the slots in that arm can receive the studs 78,78. The plank 68 is brought in contact with the weld plate 24 after the weld plate 24 has been properly positioned, as clearly illustrated in FIG. 17, for example, and a suitable clamp 88 will be utilized to fasten and force the upper arms 76 and 82 toward each other, thus putting the same force on the lower end of the plank members through the instrumentality of the studs 78 and the outside plank arm 84. As shown, a common C- clamp is illustrated at 88, but other clamps, for example VISE-GRIP pliers can also be very effectively used.

The elongated clamp 48 will remain in its clamped position until the parts have completely cured and the adjacent ends of each panel 22 are permanently bonded and integral with each other and the weld plate 24 is a permanent bonded part of the assembly. Then the clamp 88 will be removed from the upwardly extending arms 76 and 82. The inside plank member 80 will be separated from the outside plank member 86 by removing the studs 78 from the slot in the extension arm 84. The outside plank member 86 will be again turned 90 and lifted up out from between the now bonded vertical side wall panels and the side wall of the excavation.

One method of initially positioning the weld plate 24 is to temporarily fasten it to the face of outside plank 66, with double face pressure sensitive tape for exam ple, and thus bringing it into contact with the end surfaces of the abutting panels 22 at the same time the outside plank member 86 is fastened into place. Then when the weld is completed, it will take relatively little effort to free the outside plank 68 from the weld plate and the outside plank member can then be removed as described above.

It will be understood that the ends of the panels 22 which are to join at right angles at the four corners of the pool can be inserted into appropriate elbow strips 46 and solvent welded or otherwise bonded therein ei ther before or after the vertical side coplanar welding just described has been accomplished. In the usual situation, because of the flexibility of the panels, the bonding of the vertical panels can be done conveniently inside of the pool at some distance from the excavation wall, and then only the final bonding of the final coplanar joint need be performed in the close quarters as described above.

Once the side walls are all permanently bonded and permanently in place with respect to the bottom structure of the pool, reinforcing bars 89 can be introduced through vertical passages 90 provided in the vertical stiffener ribs 38. As shown in FIG. 1, these bars can extend clear down past the panels and into the ground beneath, and as shown in FIGS. 1 and 12, the upper ends of these rods 89 can be left to extend up above the panels and in position where they can be tied into a deck 99 in the manner to be described.

In order to guard against deformation of the vertical pool walls during backfilling operations and to stabilize the walls later on, when and if the water is removed from the pool, holes 92 can be drilled transversely through ribs 38 so that cables 94 can be extended therethrough and tied into the surrounding ground structure by stakes 96 which can be permanently left in v the ground. One such structure is shown in FIG. 1 and in FIG. 7, but as many such tying structures can be used as is necessary or desirable.

Another method of minimizing stress on the pool walls during backfilling is to fill the pool with water as the backfilling of earth between the excavation walls and the pool wall progress. Sufficient water will be added to the pool to create side pressure sufficient to counteract any side pressure developed by backfilling which would tend to force the side wall inwardly; but not so much water would be added as to cause the side walls to buckle or bulge outwardly. Normally this will mean that the height of water in the pool will be maintained somewhat above the height of the solid backfill as the backfilling progresses up the side of the pool.

In order to permanently stabilize and bond the adjacent panels 22, and in order to further stabilize the entire pool structure, temporary vertical concrete forms 98 will be erected around the two stiffener ribs and reinforcing bar structures immediately adjacent each weld, and the cavity formed thereby can be completely filled with concrete. The concrete will seal around the reinforcing bars above and below each of the ribs 38. After the concrete has hardened, the concrete forms 98 can either be removed or left in position.

As pointed out earlier, the clearance between the vertical side walls of the pool and the side walls of the excavation can be on the order of four to six inches. it will now be understood that this clearance need only be provided at the places where the elongated clamp 48 is used to bond panels in coplanar relationship and the clearance is only that necessary to allow the passage of the outside plank member 86 and that necessary to pro vide clearance for the vertical concrete forms 98. At all other points along the side walls, it is necessary only that the excavation be of sufficient width to accommodate the panels in their final position together with the stiffener ribs attached thereto.

Following the complete assembly of the pool as set out above, the ground is carefully and firmly backfilled against the vertical pool side walls up to approximately the height of the panels 22. Then a deck such as the deck 99, extending into the deck receiving area provided in the coping 27, is added. As shown, this deck 99 is made of poured concrete, and, as clearly seen in FIG. 12, the concrete completely fills the open, deckreceiving area 56 provided by coping 27. It also ties in the reinforcing bars 89, as seen in that figure.

Upward and downward projections 100,100 serve to firmly tie the curved top, deck-receiving flange 58 into the deck in the form of the invention illustrated. These same projections can serve as a convenient stop for a course of patio bricks or wooden decking should that be the material used for the deck. It is to be understood that additional earth or ground could also be filled in to form, in effect, a deck similar to the poured concrete deck 99 illustrated herein.

Variant Forms of the Invention In some circumstances, it will be found desirable to constitute the bottom of a swimming pool of poured concrete or similar material. The pool excavation in such a case can be of the same length and width relative to the vertical pool walls as described above, but the shape and depth of the bottom of the excavation will be such that the desired layer of concrete can be poured on top of it and then formed to the desired pool depth and contour. To construct such a pool, the vertical side walls will first be welded or bonded into a unitary structure in accordance with the aforesaid teachings of the invention, and then the concrete bottom will be poured in to encompass and come into sealing relationship to the bottom edge of the modular panels 22. This structure is illustrated in FIG. 10 wherein the panel lower lip 34 provides a sound footing and bond into the poured concrete pool bottom 102.

In some instances, the lower lip 34 will be trimmed from the bottom of the panels 22 before the panels are set in the cement bottom.

To form an even less expensive pool, the pool bottom can be constituted as the ground itself. In this situation the excavation will be prepared as explained above, the vertical side walls will be constructed in accordance with the teaching of the invention, and the lower end portions of the bottom course of panels will be set in the ground, with the ground defining the contour and shape of the pool bottom, as illustrated in FIG. 11.

Because of the permeability of the ground, this form of the invention utilizes a flexible, tough waterproof liner 104 which completely lines the entire pool structure from below the flange 58 of the coping 27. A fragmentary illustration of a portion of the side wall, the ground and the liner are shown in FIG. ll.

FIG. 14 illustrates the liner 104 in relationship to the top edge of the vertical side wallls and shows a method of fastening the liner underneath the coping. As shown, the poolside edge of the horizontal lower support wall 50 of the coping has an upstanding projection 106 thereon. The lower horizontal portion 62 of the deck receiving flange 58 is spaced from the lower support wall 50, and the projection 106, together with the portion 62 define a restricted opening into a liner locking chamber 108. As clearly seen in FIG. 14, a normally round compressible and flexible cable 110 is used to force the flexible liner 104 into the liner locking cavity where the cable 110 will prevent its accidental release. It is to be noted that as long as the flexible liner is not punctured, no moisture can pass behind it and to the pool bottom. In fact, in situations where a water imper vious deck is used, such as the concrete deck 99 for example, the pool bottom area is even protected substantially from seepage due to rain and other surface water flowage. Because of this construction, the deterioration and erosion of the contour and shape of the pool bottom which is prevalent in the case of flexibly lined pools of the above ground type, is no problem in the pool of the present invention. The below ground pool with an earth bottom will, therefore, maintain its desired contour indefinitely.

The flexible liner of this form of the invention can be made of any one of a number of waterproof substances, but a liner made of vinyl plastic has been found to be excellent for the purpose.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A below ground swimming pool in intimate supported relation to the walls of an excavation in the ground, said pool including:

a plurality of modular panels of a plastic material which is susceptible of being solvent welded;

longitudinally extending elongated fittings having slots therein to sealingly receive said panels;

some of said panels being solvent welded in edge-toedge relation to each other and some being bonded in integral, sealing relation to said fittings to form a watertight upright side wall structure laterally supported by the ground;

a continuous pool bottom wall in underlying relation to said upright wall structure;

means for preventing water loss through said bottom wall;

each of said panels having a plurality of elongated,

parallel vertical stiffener ribs integral with a back outside surface thereof, said ribs being provided with vertical passages therethrough;

elongated reinforcing bars passing through said passages to extend into the ground therebelow and also extend above said ribs;

at least some of said ribs being provided with transverse openings therethrough between said reinforcing bars and said upright side wall;

tension cables fastened through said openings and back to anchors situated in the ground at substantial distances from said ribs.

2. The combination as specified in claim 1 wherein said plurality of modular panels are situated in at least two horizontal banks of panels one situated vertically over and in sealing relation to the other; at least some of the stiffener ribs of the upper panels being in vertical alignment with corresponding stiffener ribs of the lower panels; and at least some of the reinforcing bars passing through the vertical passages of both an upper and a lower panel.

3. The combination of claim 1, and an elongated coping fastened to the top edge of said vertical side wall, said coping having a flexible downwardly extending bottom flange situated adjacent a top front inside surface of said pool wall, said flange being biased out of the vertical toward the pool wall to cause a bottom edge of said flange to lie in contacting relation to said inside wall surface despite any undulations in said wall surface.

4. The combination of claim 1 wherein the top edge of said vertical side wall is provided with an outwardly horizontally extending lip, an elongated coping is provided with a lower horizontal support wall which is fastened to said lip, said coping having a deck receiving flange extending upwardly from said lower support wall and defining a deck receiving area open away from the edge of said pool, and a deck having an inside edge por tion encompassed by said deck receiving flange, said deck extending outwardly from the pool around the edge thereof.

5. The combination of claim 4 wherein said reinforcing bars extend upwardly into said deck and said deck is made of poured concrete which, when hardened, is sealingly fastened into the deck receiving flange and encompasses the upper ends of said bars and supports them against lateral movement.

6. The combination as specified in claim 5 wherein said plurality of modular panels are situated in at least two horizontal banks of panels one situated vertically over and in sealing relation to the other; at least some of the stiffener ribs of the upper panels being in vertical alignment with corresponding stiffener ribs of the lower panels; and at least some of the reinforcing bars passing through the vertical passages of both an upper and a lower panel. 

1. A below ground swimming pool in intimate supported relation to the walls of an excavation in the ground, said pool including: a plurality of modular panels of a plastic material which is susceptible of being solvent welded; longitudinally extending elongated fittings having slots therein to sealingly receive said panels; some of said panels being solvent welded in edge-to-edge relation to each other and some being bonded in integral, sealing relation to said fittings to form a watertight upright side wall structure laterally supported by the ground; a continuous pool bottom wall in underlying relation to said upright wall structure; means for preventing water loss through said bottom wall; each of said panels having a plurality of elongated, parallel vertical stiffener ribs integral with a back outside surface thereof, said ribs being provided with vertical passages therethrough; elongated reinforcing bars passing through said passages to extend into the ground therebelow and also extend above said ribs; at least some of said ribs being provided with transverse openings therethrough between said reinforcing bars and said upright side wall; tension cables fastened through said openings and back to anchors situated in the ground at substantial distances from said ribs.
 2. The combination as specified in claim 1 wherein said plurality of modular panels are situated in at least two horizontal banks of panels one situated vertically over and in sealing relation to the other; at least some of the stiffener ribs of the upper panels being in vertical alignment with corresponding stiffener ribs of the lower panels; and at least some of the reinforcing bars passing through the vertical passages of both an upper and a lower panel.
 3. The combination of claim 1, and an elongated coping fastened to the top edge of said vertical side wall, said coping having a flexible downwardly extending bottom flange situated adjacent a top front inside sUrface of said pool wall, said flange being biased out of the vertical toward the pool wall to cause a bottom edge of said flange to lie in contacting relation to said inside wall surface despite any undulations in said wall surface.
 4. The combination of claim 1 wherein the top edge of said vertical side wall is provided with an outwardly horizontally extending lip, an elongated coping is provided with a lower horizontal support wall which is fastened to said lip, said coping having a deck receiving flange extending upwardly from said lower support wall and defining a deck receiving area open away from the edge of said pool, and a deck having an inside edge portion encompassed by said deck receiving flange, said deck extending outwardly from the pool around the edge thereof.
 5. The combination of claim 4 wherein said reinforcing bars extend upwardly into said deck and said deck is made of poured concrete which, when hardened, is sealingly fastened into the deck receiving flange and encompasses the upper ends of said bars and supports them against lateral movement.
 6. The combination as specified in claim 5 wherein said plurality of modular panels are situated in at least two horizontal banks of panels one situated vertically over and in sealing relation to the other; at least some of the stiffener ribs of the upper panels being in vertical alignment with corresponding stiffener ribs of the lower panels; and at least some of the reinforcing bars passing through the vertical passages of both an upper and a lower panel. 